Discrimination between poultry eggs on the basis of some observable quality is a well-known and long-used practice in the poultry industry. "Candling" is a common name for one such technique, a term which has its roots in the original practice of inspecting an egg using the light from a candle. As is known to those familiar with poultry eggs, although egg shells appear opaque under most lighting conditions, they are in reality somewhat translucent, and when placed in front of a direct light, the contents of the egg can be observed.
In most practices, the purpose of inspecting eggs, particularly "table eggs" for human consumption, is to identify and then segregate those eggs which have a significant quantity of blood present, such eggs themselves sometimes being referred to as "bloods" or "blood eggs." These eggs are less than desirable from a consumer standpoint, making removal of them from any given group of eggs economically desirable.
U.S. Pat. Nos. 4,955,728 and 4,914,672, both to Hebrank, describe a candling apparatus that uses infrared detectors and the infrared radiation emitted from an egg to distinguish live from infertile eggs.
U.S. Pat. No. 4,671,652 to van Asselt et al. describes a candling apparatus in which a plurality of light sources and corresponding light detectors are mounted in an array, and the eggs passed on a flat between the light sources and the light detectors.
In many instances it is desirable to introduce a substance, via in ovo injection, into a living egg prior to hatch. Injections of various substances into avian eggs are employed in the commercial poultry industry to decrease post-hatch mortality rates or increase the growth rates of the hatched bird. Similarly, the injection of virus into live eggs is utilized to propagate virus for use in vaccines. Examples of substances that have been used for, or proposed for, in ovo injection include vaccines, antibiotics and vitamins. Examples of in ovo treatment substances and methods of in ovo injection are described in U.S. Pat. No. 4,458,630 to Sharma et al. and U.S. Pat. No. 5,028,421 to Fredericksen et al., the contents of which are hereby incorporated by reference as if recited in full herein. The selection of both the site and time of injection treatment can also impact the effectiveness of the injected substance, as well as the mortality rate of the injected eggs or treated embryos. See, e.g., U.S. Pat. No. 4,458,630 to Sharma et al., U.S. Pat. No. 4,681,063 to Hebrank, and U.S. Pat. No. 5,158,038 to Sheeks et al. U.S. Patents cited herein are hereby incorporated by reference herein in their entireties.
In ovo injections of substances typically occur by piercing the egg shell to create a hole through the egg shell (e.g., using a punch or drill), extending an injection needle through the hole and into the interior of the egg (and in some cases into the avian embryo contained therein), and injecting the treatment substance through the needle. An example of an injection device designed to inject through the large end of an avian egg is disclosed in U.S. Pat. No. 4,681,063 to Hebrank; this device positions an egg and an injection needle in a fixed relationship to each other, and is designed for the high-speed automated injection of a plurality of eggs. Alternatively, U.S. Pat. No. 4,458,630 to Sharma et al. describes a bottom (small end) injection machine.
In commercial poultry production, only about 60% to 90% of commercial broiler eggs hatch. Eggs that do not hatch include eggs that were not fertilized (which may include rots), as well as fertilized eggs that have died (often classified into early deads, mid-deads, rots, and late deads). Infertile eggs may comprise from about 5% up to about 25% of all eggs set. Due to the number of dead and infertile eggs encountered in commercial poultry production, the increasing use of automated methods for in ovo injection, and the cost of treatment substances, an automated method for identifying, in a plurality of eggs, those eggs that are suitable for injection and selectively injecting only those eggs identified as suitable, is desirable.
U.S. Pat. No. 3,616,262 to Coady et al. discloses a conveying apparatus for eggs that includes a candling station and an inoculation station. At the candling station, light is projected through the eggs and assessed by a human operator, who marks any eggs considered non-viable. Non-viable eggs are manually removed before the eggs are conveyed to the inoculating station.